Welcome to the noob's guide to vertex manipulation as I am partially a noob at it.
Before we start, download Jackhammer
Thank you... now set it up, if you haven't already.
Alright, i guess we are ready to begin!
Many people say that Vertex Manipulation, when not used properly, causes errors. And i'm here to teach you how to use it properly.
There's one key thing for you to know:
If you want to literally bend brushwork to your will, use triangles, not cubes.
OK, let's go ahead onto the making of something i accidentally discovered:
Make a brush with dimensions like: 64x64, 32x32, 16x16, 128x128 etc. just keep the second number the same as the first one.
At first, it must have the null texture, in order for optimization.
OK, now, most of this can be done in the 3D view, so let's select our cube, and go to the always-hated VM Tool.
Alright, press the icon again if you still have the yellow and white dots, until you have the white ones, because those are the vertices themselves, and select them "diagonally" but only on one side:
My evil plan is working, muahaha! Now press Ctrl+F (without the +) and look what happens:
Ta-da! The faces are split, but do not enter the Select Tool, otherwise you're cancelling what you just did.
Go ahead with the other faces (only the sides, not the bottom and the top):
Ah, reminds me of my first box in 3ds Max...
Select the top vertices only:
Now, this is why i told you to install Jackhammer.
Find the center of the 4 vertices, and rotate them by 45 degrees, by holding right click.
The GIF is a bit different, but never-mind that. So you should get this:
And now, Alt+P, if it shows errors you probably rotated it under a bigger angle than 45, or you probably didn't split faces in the same direction, or perhaps you just didn't rotate it clockwise/counter-clockwise (depends how you cut the faces).
And if it's error-free, then you can proceed:
Select the brush, and copy them above each other, but one by one, and rotate them so they fit onto each other and act as a one single brush, which is in fact, this:
Quake quality, eh?
Just remember, if you want it smoother, the height should of the original brush should be re-sized in half, and you must rotate it a lot less (15 degrees, let's say, instead of 45).